This compact (0.45″×0.6″) U1V11F5 switching step-up (or boost) voltage regulator efficiently generates 5 V from input voltages as low as 0.5 V. Unlike most boost regulators, the U1V11F5 offers a true shutdown option that turns off power to the load, and it automatically switches to a linear down-regulation mode when the input voltage exceeds the output. The pins have a 0.1″ spacing, making this board compatible with standard solderless breadboards and perfboards.
That depends on exactly how high the VIN is on the Regulator.
If the input voltage into the regulator is less than 3.3V, then that’s no problem. You won’t have to worry about damage to the Pico.
If the voltage is any higher, than you will need to put a transistor or MOSFET between the SHDN and GPIO pins. Those pins are rated to 3.3V and while you might be able to get away with 3.5V, at 4V or higher you would be in trouble.
A small N-Channel MOSFET should be sufficient to protect the GPIO.
